Energy conservation in radio systems



-rJJ-IJ ar( FIPSIOE 0R 293699239 if; Feb- 13, 1945 c. w. HANsELl. 2,369,230

ENERGY CONSERVATION IN RADIO SYSTEMS Original Filed Dec. 5l, 1940 RESONANTELAY 057: AND

FREOUENC' Y INVENTOR CLA/Q NCE W.' A/vsE/.L BY v l Mww/L/ ATTORNEY Patented Feb. 13, 1945 UNITED discapacitados;

STATES PATENT OFFICE ENERGY CONSERVATION IN RADIO SYSTEM Clarence W. Hansell, Rocky Point, N. Y., assignor to Radio Corporation of America, a corporation of Delaware 8 Claims.

The present application is a division of my application #372,636, led December 31, 1940, and relates to radio communication systems and, more particularly, to a method of and a means for conserving the amount of energy utilizedby such systems while, at the same time, ycontinuously maintaining saidrsystem in an operative condition.

In many radio communication systems, particularly those which are to be operated at carrier frequencies above 30 megacycles, a problem often arises in respect to the cost and inconvenience of maintaining the equipment always in a condition to operate. In radio relaying systems by means of radio frequency amplifiers connected between receiving and transmitting antennas, for example, it must always b`e possible to transmit signals through the system at will and yet, in many cases, the percentage of total time in which communication is desired may be small. As a consequence, in previously known types of equip'- ment, of which I am aware, it is necessary to keep the ampliiier equipments of the relay system energized continuously even though they may be used only a part of the time. In other applications, such as radio telephone systems to replace Wire line telephone exchanges, particularly those systems which may serve rural districts around small towns, through central exchanges in the towns, one of the lgreatest obstacles to be overcome has been that of maintaining equipment at the farm home always in condition to respond to calls even though the percentage of time during which the equipment may be used is very small. When calls are to be made from the farm home to the central exchange the farmer may be expected to energize his equipment before using it and to de-energize it when the conversation is finished. However, a much more difficult problem arises in keeping the subscribers equipment energized suiiiciently for calling or ringing from the central exchange. 'Ihis requires continuous power input of some amount and, over a long period of time, presents a problem in supplying the power. Ordinarily, it is desired that the subscribers equipment be capable of takingr its power from a b'attery' of moderate size. The power demand for a period of several months to a year for operating radio telephone equipment might be supplied from dry cell batteries or from a single charging of a 6 volt, 100 ampere hour storage battery if it is possible to substantially eliminate the need for any appreciable amount of stand-by power to keep the equipment in condition for calling or ringing when not actually in use.

It is, therefore, an object of the present invention to provide means for use in systems as above described by which the stand-by power requirements may be reduced while, at the same time, the

equipment is continuously maintained in a condition to receive calls from other stations.

This may be accomplished, in accordance with my invention, by employing means for energizing a minimum amount of the equipment required for calling purposes for only very short time periods repeated at su'liciently frequent intervals. During the energized periods if radio frequency input is received from the central oiice this input may serve to hold the equipment continuously energized and to cause the operation of a bell or other signal device. If the subscriber does not answer the call the central oice may return the subscribers equipment to the standby condition by merely removing the radio frequency energy which is being transmitted from the central transmitter to the subscribers eq/uipment.

In accordance with one aspect of the present invention, the subscribers equipment may be energized for calling purposes momentarily at spaced time periods by utilizing a low pressure gaseous discharge gap inserted between the power source and the radio equipment and placing a condenser across the circuit on the load side of the gap. The gaseous discharge gap provides a device which changes almost instantly from an insulator to a low resistance conductor if the potential across it exceeds a critical value and which returns to an insulating condition as soon as the current through it and the potential across it falll to some other critical value. By this means the condenser is charged periodically through the gap and discharged first through the radio frequency equipment and then through a high leakage resistance down to a point where the gap again breaks down. By this means it is possible to energize the rminimum amount of radio equipment required for ringing for periods of, for example, 0.01 second at intervals of 10 to l5 seconds. By this means the average stand-by power required may Ibe reduced by a factor of 1000 to l compared with the power required for continuously energizing the equipment for calling. i

'I'he present invention will be more fully understood by reference to the following detailed description which is accompanied by a drawing in which Figure l illustrates one form of my invention particularly useful for ultra-short wave radio telephone systems, while Figures 2 and 3 illustrate modifications of the form of the invention shown in Figure 1.

A form of the present invention is shown in Figure l, which is a schematic diagram of a radio telephone station, such as might be employed at a farm home to communicate through a central telephone exchange. Naturally similar arrangements may be used at any radio telephone station at which it is desired to be able to receive calls at any time without requiring more than a minimum of standby power consumption. In this diagram I have shown an antenna. system 21 supplying radio frequency energy to a superheterodyne type ra-dio receiver employing a heterodyne detector 28, a, heterodyne oscillator 29, intermediate frequency amplifiers, a second detector 30, an audio amplifier 3| and a receiver 32. This gure also shows in block form a radio transmitter 34 connected to an associated antenna 35. I have indicated the transmitter input by a conventional microphone 36.

All of the receiving and transmitting equipment shown in this figure is energized by a cathode supply battery 38 and an anode supply battery 39. Battery 38 may be of the 6 volt storage battery type while battery 39 may be a 180 volt dry battery. Control electrode bias batteries may be employed, if desired, though they have not been illustrated in this figure. When the equipment is in the standby condition only the cathodes of the first portions of the receiver are energized and these portions employ vacuum tubes of the lowest obtainable cathode and anode power demand. The tubes in this portion of the receiver are not continuously energized with full anode potential but have substantially full anode potential supplied in pulses of perhaps 1 or 2 seconds duration repeated at intervals of from to 20 seconds. This is accomplished by supplying anode currents to these portions of the equipment over a relatively large condenser 40 which is charged at intervals.

Condenser 40 is charged through a gaseous discharge tube 4| which may be a low pressure neon tube or a neon lamp having no resistance in series therewith. After the condenser is charged from source 39 through the gas discharge tube 4| the current through tube 4| drops to such a low value that the discharge is extinguished. The condenser then discharges through the vacuum tube anode circuits within portions 28, 29 and 3| of the receiver, first, at normal anode current values and then with diminishing current values until, finally, the discharge is at a relatively slow rate. Eventually, the potential across the condenser 40 reaches Such a low value and the potential acrossthe neon tube 4| therefore reaches such a high value that another discharge through tube 4| takes place recharging the condenser. This repeated charging and discharging of the condenser takes place continuously during all time periods when the equipment is not in use. If it should be desired to call the station of Figure 2, the central exchange station radiates a carrier wave of the frequency to which the receiver is tuned and which is modulated at a characteristic frequency of, say, 40 cycles. During periods when the condenser is charged the fully energized portions of the receiver, that is, portions 28, 29 and 30, deliver 40 cycle current to a resonant relay 42 which is resonant to 40 cycles. Vibrations of the responsive element of the resonantI relay energize winding 43 of a slow acting relay 44 to close contacts 45 and 46. The closure of contacts 45 energizes a call bell 41.

Since it is desirable that the slow acting relay 43 should close relatively quickly and open relatively slowly, the contacts 46 short-circuit a coil 48 when the relay is energized. Short-circuited coil 48 tends to prevent the collapse of the magnetic flux in the core of relay 44 and thus the contacts are held closed for some time after the winding 43 is actually deenergized. 4Other electrical or mechanical arrangements may be utilized to accomplish the same purpose, if desired.

The subscriber, hearing the ringing of bell 41,

removes earphone 32 from the hook 49, thus vclosing contacts 4D, and automatically energizing the cathodes of the tubes in amplier 3| and the tubes in transmitter 34 and in so doing allows anode current to flow in them. The same operation energizes winding 5| of relay 52 closing contacts 53 across the neon tube 4| and thereby continuously energizes the anodes of the entire receiver. The operation of removing receiver 32 from its hook also opens contact 54 and deenergizes bell 41. The subscriber may then reply to the calling ofce by means of microphone 36 and transmitter 34. The conversation may then be carried on in the conventional manner. Replacing of the earphone 32 automatically deenergizes the transmitter and most of the receiving equipment and returns the remainder of the receiver to the condition for again receiving calls.

It will be noted that as long as the batteries 38 and 39 are in good condition the neon tube 4| flashes at regular intervals. Tube 4| may, therefore, be mounted in such a position that it may be easily visible and the condition of the batteries may be checked at any time. It is to be assumed that in giving the equivalent of rural party line service a number of receivers may be adjusted to operate on a common radio carrier frequency and the corresponding transmitters all operate on another common radio carrier frequency. Selective calling may then be accomplished by means of different calling modulation frequencies, such as 35, 40, 45 and 50 and 55 cycles per second, each receiver being equipped with a resonant relay 42 tuned to its particular frequency.

The system may equally well be employed for telephone by amplitude, phase or frequency modulation of the radio carrier and by systems employing various sub-carrier combinations.

While I have shown a superheterodyne type of receiver it may not be necessary in all cases to use this type but the receiver may be a tuned radio frequency receiver, a 'super-regenerative receiver or any other suitable type.

Another form of application of the invention is shown in Figure 2. In this arrangement I have shown a multistage secondary emission type of amplifier including a cathode 6| which is preferably of very minute dimensions, a rst anode 62 having a hole or slit therein for forming a stream of electrons and a control electrode 63 for deflecting the beam of electrons to vary the number thereof which impinge on surface 65. Secondary electrons are emitted as a result of the electrons impinging on surface 65 and 0n successively later secondary emitting surfaces 66 at successively higher potentials. Each surface emits more electrons than impinge thereon and thus give an increasing current in successively later stages. The successively higher potentials on the different emitting surfaces 66 are supplied through taps on a voltage divider 61'. Finally, after being greatly increased in strength the current is terminated on an anode 68. A screen electrode 68' may be provided before anode 68 to prevent the escape of secondary electrons from anode 68. Amplifiers of this general type are often known in the art as electron multipliers. The anode current is varied or modulated in accordance with high frequency input to the control electrode 63. The high frequency ble in loudspeaker 85.

input to control electrode 63 is supplied thereto through a coupling circuit 69 from an antenna 10. A portion of the high frequency output from the secondary emission amplifier 66 is applied l through coupling circuit 1| to a suitable rectifier '|2 which is preferably a fixed type of crystal detector or a copper oxide type of rectifier where it is rectified into direct current. Output from the rectifier or detector 12 is applied to winding 13 of a relay '14 to operate contact arms 15, 16

into engagement with contacts 'Il and 18. The operation of contact arms 15, 'I6 into contact with 11, 18 controls power input to the secondary emission amplifier 66 and an associated radio receiver 86. Since the secondary emission amplifier 66 is shown as normally not energized with input power potentials, means are provided for momentarily applying impulses of power. This consists of a gaseous discharge tube 8| which breaks down and carries electricalfcurrent freely if a potential is applied thereacross which is above a certain value less than the power source potential. Assuming a direct potential is applied from sources 82, the gaseous discharge tube breaks down and passes current to charge a condenser 83 and then open circuits itself as the condenser becomes fully charged. From the condenser 83 potentials are applied to the electrodes of the secondary emission amplifier 66 by way of the voltage divider network l6l.

In series with the gaseous discharge tube is a winding 84of relay 14. The discharge current closes the contacts of the relay 'I4 momentarily energizingthe cathode 6| of the secondary emission amplifier and allowing the amplifier to function. If there is no incoming radio frequency carrier from 'I6 the relay falls open again when the discharge current has ceased. The condenser then slowly discharges through the voltage di, vider network 61 which is preferably made of a material called Thyrite so that the rate of condenser discharge will decrease to a low value as the potential falls. After the potential across the condenser 83 drops to a low level the potential across the gaseous discharge tube 8| is again low enough to cause another breakdown and current discharge. Thus, at intervals of from 15 seconds, or so, the'amplier is energized for .61 to .1 second.

If now, a carrier wave current is delivered to the secondary emission amplifier from antenna 16, then this current will be amplified and rectified when the amplifier is energized. The rectified high frequency current will then hold the relay 14 closed through winding 13 and keep the amplifier energized continuously. The relay also starts up a receiver 86 by the closure of contacts 15, l1 by means of which modulations of the received carrier wave may be made audi- The contacts 15, 'Il are preferably equipped with time delay closing by means of devices known in the art.

In Figure 3 I have shown another means for energizing an amplifier and detector momentarily at spaced time intervals in combination with means for calling by means of a bell. In this system, a secondary emission amplifier 66 is used as before but the amplifier also serves as a de' tector to operate a relay 86 through winding 81 to close contacts 88, 89 and ring bell 4l. In the arrangement shown in this figure all of the power for the calling and ringing system is obtained from a single low voltage battery 96. Current from the battery is passed through the primary winding 9| of an induction coil transformer 92 in CTI fil

series with an instantaneous opening but slow closing contact arrangement 93, 94 actuated by the magnetic field of the induction coil 92. The contact is made slow closing by means of a pawl carried by contact arm 94 engaging ratchet wheel 96. The ratchet wheel may be supplied with a suitable time delay mechanism such as a iiuid friction device, a mechanical governor or a clock escapement to allow it to turn freely but only slowly. In some cases suicient time delay may be obtained merely by making ratchet Wheel 96 heavy.

Each time the induction coil contacts 93, 94 close they momentarily energize the cathode 6I of the amplifier 66, raising its temperature high enough to cause electron emission and then the contacts are pulled open by the magnetic field of the induction coil 92. the contacts permits them to open with little, if any, arcing and slows up the decrease of current in the primary winding 9| of the induction coil. The decreasing current in the primary winding and collapse of the magnetic field through coil 9| energizes the secondary emission amplifier electrodes 62, 65, 66 and 68 momentarily .by induction into the secondary winding 96 of the induction coil 92. If there is no radio frequency input to the secondary emission amplifier 66 from antenna |66, the application of the electrode potentials causes a momentary flow of current in the anode circuit and a weaker pulse in the circuit of screen electrode 68'. If there is a radio frequency input caused by appli-cation of carrier current from the district central transmitter, then a radio frequency potential will be built up across the circuit |6| which is tuned to the central transmitter frequency and which is in series with anode 68. This high frequency potential reduces the magnitude of the pulse of direct anode current and increases the pulse of screen electrode current. The anode and screen currents are utilized to energize windings 81 and |62 of polarized relay 86 which is thrown to and remains in one position, or another, depending on whether the central station transmitter is energized and operated at the frequency corresponding to calling the particular subscribers station. A third winding |63 is provided on the core of relay 86 in order to make the armature 88 slow to operate in one position, as described with reference to relay 44 in Figure 1. If the induction coil is designed to provide impulses about once every 15 seconds,

- then the bell 41 will ring at 15 second intervals while the subscribers station is being called until the subscriber answers the call by operating switch |64, thus energizing his radio receiving and transmitting equipment |65. Thus, the calling unit at the subscribers station, in this modiiication, is made a separate accessory which may be provided, or not, according to need.

After the subscriber has thrown switch |64 so that his receiver and transmitter are energized he may communicate with the central station in the usual manner and through the central station to other individual stations. Antennas |66 and |66 are preferably directional antennas in order to reduce the power requirements as much as possible. The single battery 90 will operate the system for a long time on one charge. The battery may be kept charged by any of the conventional means such as a wind operated battery charger. Wave, tide or temperature operated generators may also be used for charging.

While I have particularly shown and described A condenser 9`| across f`by signal responsive means substantially conseveral modifications of my invention, it is to be distin-ctly understood that my invention is not limited thereto but that improvements within the scope of the invention may be made.

I claim:

l. A communication station comprising standby signal responsive means substantially continuously in an operative condition, said means requiring little power for its operation, further signal receiying andMtransmlttingmmeans requiring substantially greater amounts of power for operation, said means being normally de-enere gized and means responsive to receipt of signals by said standby means for energizing said receiving and transmitting means, said signal responsive means being intermittently energized solely by energy stored in a condenser, the said energy being supplied to said condenser in short pulses, the time of initiation of said pulses being deter- /mined by the energy level in said condenser. 2. A communication station comprising standtinuously in an operative condition, said means -requiring little power for its operation, further signal receiving and transmitting means requiring substantially greater amounts of power for operation, said means being normally de-energized and means responsive to receipt of signals by said standby means for energizing said receiving and transmitting means, said signal responsive means .being energized .by energy stored in a condenser, and means for applying short pulses of energy to said condenser from a primary source of energy at spaced time intervals, the time duration of said pulses being substantially less than the time of energization oi said signal responsive means and the said energy being supplied to said condenser in short pulses, the time of initiation of said pulses being determined by the energy level in said condenser.

3. A communication station comprising standby signal responsive means substantially continuously in an operative condition, said means requiring little power for its operation, further signal receiving and .transmitting means requiring substantially greater amounts oi power for operation, said means being normally de-energized and means responsive to receipt of signals by said standby means for energizing said receiving and transmitting means, said signal re-` sponsive means being energized by energy stored in a condenser, a primary source of energy, a gas discharge tube connected between said source and said condenser and so arranged that discharge of said condenser below a predetermined charge causes said tube to become conductive and charge said condenser.

4. A communication station comprising standby signal responsive means substantially continuously in an operative condition, said means requiring little power for its operation, further signal receiving and transmitting means requiring substantially greater amounts of power for operation, said means being normally de-energized and means responsive to receipt of signals by said standby means for energizing said receiving and transmitting means, said signal responsive means being energized by energy stored in a condenser, a primary source of energy, a gas discharge tube connected between said source and said condenser and so arranged that discharge of said condenser below a predetermined charge causes said tube to become conductive and charge said condenser, and means for disabling said call signal and short-circuiting said gas discharge tube.

5. A communication station comprising signal responsive means, means for intermittently supplying energy to said signal responsive means, said energy supplying means including energy storage means and being intermittently supplied with pulses of energy through a cyclically completed path from a source of energy, and means responsive to the receipt of signals by said signal responsive means for locking said cyclically completed path in a continuously conducting condition so that energy is continuously supplied to said signal responsive means, the time of cyclic 4closure of said path being of substantially shorter duration than the repetition time of said cyclic closure.

- 6. A communication station comprising signal responsive means, means for intermittently supplying energy to said signal responsive means, said energy supplying means being intermittently provided with pulses of energy from a source and means responsive to the receipt of signals by said signal responsive means for so altering the operation of said energy supplying means .that energy is continuously supplied to said signal responsive means, said energy supplying means including a condenser and a gas discharge tube connected between said condenser and said source and so arranged that discharge of said condenser below a predetermined charge causes said gas tube to become conductive and charge said condenser.

7. A communication station comprising signal responsive means including an electron multiplier tube, means for intermittently supplying energy to said multiplier tube, said energy supplying means being intermittently provided with pulses of energy from a source and means responsive to the receipt of signals by said signal responsive means for so altering the operation of said energy supplying means that energy is continuously supplied to said electron multiplier tube, the said energy being supplied to energy storage means, the time of initiation of said pulses being determined by the level of the energy in said storage means.

8. A communication station comprising signal responsivemeans including an electron multiplier tube, means for intermittently supplying energy to said multiplier tube, said energy supplying means being intermittently provided with pulses of energy from a source and means responsive to .the receipt of signals by said signal tube to become conductive and charge said condenser.

CLARENCE W. HANSELL. 

